1. Field of the Invention
The present invention generally relates to a method for filtering signals, in particular, to a method for filtering signals of a touch sensitive device.
2. Description of Related Art
The progress of the information science and technology provides the people with more convenient products and more comfortable life styles. Now, various information products, such as mobile phone, computer and personal digital assistant (PDA) are everywhere, so that our daily life would be unimaginable without these information products. In order to make the portable information products have a more-humanized operation interface, it is the current trend to integrate a touch panel or a stylus into an information product.
The touch sensitive device in the most common use is mainly categorized into a resistive touch sensitive device and a capacitive touch sensitive device, wherein the capacitive touch sensitive device works mainly based on sensing a signal according to a so-called capacitance electrical characteristic. When two electric conductor layers are not touched by each other but close to each other, the electric fields thereof are inter-acted to form a capacitor. In fact, the surfaces of the upper layer and the lower layer in a touch panel structure are two conductive layers respectively comprising a plurality of conductive layer formed by interlaced conductive traces of electrodes. Note that a human finger is an electric conductor. When a finger is put on a touch panel, a tiny capacitor is generated between the conductive traces of electrodes and the finger, and a microprocessor is used to detect the touch position of the finger of a user by sensing the capacitance variations.
Since a capacitive touch sensitive device is easily caused to produce noise caused by environment variations, such as high-frequency interference source, temperature variation or electrostatic discharge (ESD); consequently, abnormal sensed signals (noise) are produced with the capacitive touch sensitive device, which trigger a fault judgment with the electronic device and waste the electrical power.